On Board Diagnostics II PCED

1999 PCED On Board Diagnostics II

SECTION 5: Pinpoint Tests

H: Fuel Control

H20 PERFORM KOER SELF-TEST

Key on, engine running and engine at operating temperature.
Activate Key On, Engine Running (KOER) Self-Test.

Is DTC P1127, P1128 or P1129 present during KOER Self-Test?

Yes	No
GO to Section 4 , Powertrain Diagnostic Trouble Codes (DTC) Charts and SERVICE DTC P1127, P1128 or P1129.	GO to H21 .

H21 DIAGNOSTIC TROUBLE CODE (DTC) P0133 AND P0153: HO2S RESPONSE TEST

DTC/HO2S Reference List:

DTC P0133 = HO2S-11
DTC P0153 = HO2S-21

Key on, engine off.
Select Generic OBD II Function from the menu and trigger.
Press Continue.
Select Diagnostic Monitoring Test Results from the menu and trigger.
Scroll to Test ID: 01 trigger and press start.
Key off.

Does the measured value indicate greater than 614?

Yes	No
COMPLETE PCM Reset to clear DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2 , Drive Cycles). REPEAT Test Step H20 . If test results indicate a pass, testing is complete.	GO to H22 .

H22 CHECK FOR SOURCE OF POTENTIAL HO2S CONTAMINATION

Investigate the following items as potential sources of HO2S contamination:

Use of unapproved silicon sealers.
Fuel contaminated by silicon additives.
Excessive oil burning (i.e. rings, valve seals and oil overfill).
Glycol (antifreeze) leaking internally in the engine.
Lead contaminated fuel.
Short drive cycles in cold weather.
Use of unapproved cleaning agents.

Are any of the above conditions present?

Yes	No
REPAIR source of contamination. REPLACE HO2S and oil/filter. COMPLETE PCM Reset to clear DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2 , Drive Cycles).	GO to H23 .

H23 CHECK FOR UNMETERED AIR LEAKS

Fuel calculations can be affected by unmetered air leaks.

Carefully inspect the following areas for potential air leaks:

Hoses connecting to MAF sensor assembly.
Hoses connecting to throttle body.
Intake manifold gasket leaks.
PCV disconnected.
Vacuum lines disconnected.
Improperly seated engine oil dipstick and tube.
Exhaust leaks at flanges and gaskets.

Is there any air leaks?

Yes	No
REPAIR source of air leak. COMPLETE PCM Reset to clear DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2 , Drive Cycles).	GO to H24 .

H24 CHECK HO2S CIRCUIT WIRING

Note: Refer to the PCM connector pin number in the beginning of this pinpoint test.

Disconnect suspect HO2S.
Jumper HO2S signal to VPWR at the HO2S harness connector.
Key on, engine off.

Note: HO2S displayed as O2S on Scan Tool.

Access the correct HO2S PID.

Is the voltage greater than 1.50 volts?

Yes	No
KEY OFF. REPLACE HO2S. CHANGE oil/filter. COMPLETE PCM Reset to clear DTCs. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2 , Drive Cycles).	KEY OFF. REMOVE jumper wire. GO to H25 .

H25 CHECK HO2S SIGNAL AND SIGNAL RETURN CIRCUITS FOR OPEN IN HARNESS

Measure resistance of HO2S Signal circuit between PCM harness connector pin and HO2S harness connector.
Measure resistance of HO2S Signal RTN circuit between PCM harness connector pin and HO2S harness connector.

Is the resistance less than 5.0 ohms?

Yes	No
GO to H26 .	REPAIR open circuit. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2 , Drive Cycles).

H26 CHECK HO2S CIRCUIT FOR SHORT TO VPWR IN HARNESS

Measure resistance between the HO2S Signal and VPWR circuit at the PCM harness connector pin.

Is the resistance greater than 10,000 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM). COMPLETE HO2S Monitor Repair Verification Drive Cycle (REFER to Section 2 , Drive Cycles).	REPAIR short circuit. COMPLETE HO2S Monitor Drive Cycle (REFER to Section 2 , Drive Cycles).

H27 DTC P0131 AND P0151: CONTAMINATED HO2S / VOLTAGE SHIFT

DTC P0131 = HO2S-11
DTC P0151 = HO2S-21

Check for water in HO2S connector.

Is there water in the HO2S connector?

Yes	No
REPAIR source of water entry. Dry out connector. REPLACE HO2S.	GO to H28 .

H28 VERIFY WIRING IS IN PROPER PIN LOCATION

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Measure resistance of the HO2S Signal circuit and HO2S Signal Return circuit between the PCM harness connector pin and the HO2S harness connector.

Is the resistance less than 5.0 ohms?

Yes	No
REPLACE HO2S.	REPAIR as necessary.

H30 DTCS P0135, P0141 and P0155 AND P0161: HO2S HEATER CIRCUIT IS OPEN, SHORTED TO GROUND, SHORTED TO VPWR OR EXCESSIVE CURRENT DRAW

Note: Refer to the PCM harness connector pin numbers in the beginning of this pinpoint test.

DTC/HO2S Reference List:

DTC P0135 = HO2S HTR-11
DTC P0141 = HO2S HTR-12
DTC P0155 = HO2S HTR-21
DTC P0161 = HO2S HTR-22

Note: On some applications, a vehicle hoist is required to access the HO2S harness.

Visually inspect the HO2S circuit for exposed wiring, contamination, corrosion and proper assembly.

Were any concerns found during the visual inspection?

Yes	No
REPAIR any concerns found in the visual inspection.	GO to H31 .

H31 PERFORM KEY ON ENGINE OFF (KOEO) SELF-TEST

Key on, engine off.
Perform KOEO Self-Test.

Is DTCs P0135, P0141, P0155 or P0161 present?

Yes	No
KEY OFF. GO to H32 .	Unable to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 .

H32 CHECK VPWR VOLTAGE TO H02S HARNESS CONNECTOR

Note: If DTCs P0135 and P0155 or P0141 and P0161 are displayed, both heater circuits will require testing. DTCs displayed separately are tested individually.

Disconnect the appropriate HO2S(s).
Key on, engine off.
Measure voltage between VPWR and SIG RTN circuits at the HO2S harness connector.

Is the voltage greater than 10.5 volts?

Yes	No
KEY OFF. GO to H33 .	CHECK fuse in circuit. If fuse is OK, REPAIR open circuit. For no VPWR on LS6/LS8: GO to Pinpoint Test B5 .

H33 CHECK HO2S HEATER RESISTANCE

Measure the resistance of the HO2S heater (refer to schematic at the beginning of this Pinpoint Test).

Is the resistance between 3 and 30 ohms?

Yes	No
GO to H34 .	REPLACE HO2S.

H34 CHECK HO2S CASE FOR SHORT TO VPWR AND HEATER GND

Measure resistance between HO2S Heater GND pin at HO2S connector and the HO2S case.
Measure resistance between the HO2S Heater GND pin and the SIG RTN Pin at the HO2S sensor.
Measure the resistance between the HO2S VPWR pin at the HO2S connector and the HO2S case.

Is the resistance greater than 10,000 ohms?

Yes	No
GO to H35 .	REPLACE HO2S.

H35 CHECK HO2S HEATER CIRCUIT FOR SHORT TO VPWR AND GND

Disconnect PCM.
Measure resistance between the suspect HO2S HTR circuit and PWR GND circuit at the HO2S harness connector.
Measure resistance between the suspect HO2S HTR circuit and SIG RTN circuit at the HO2S harness connector.
Measure resistance between the suspect HO2S HTR circuit and VPWR circuit at the HO2S harness connector.

Is each resistance greater than 10,000 ohms?

Yes	No
GO to H36 .	REPAIR shorted circuit.

H36 CHECK HO2S HEATER CIRCUIT FOR OPEN IN HARNESS

Measure resistance of the suspect HO2S HTR circuit between PCM harness connector pin and HO2S harness connector.
Measure the resistance of the suspect HO2S HTR circuit between PCM harness connector pin and ground.

Is the resistance less than 5.0 ohms between the the HO2S harness connector and the PCM; and greater than 10,000 ohms between the PCM and the ground?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPAIR open or shorted heater circuit in harness.

H40 DTCs P1131, P1132, P1151 AND P1152: UPSTREAM HO2S NOT SWITCHING. DTCs P1130 and P1150: FUEL SYSTEM NOT SWITCHING AT FUEL TRIM (RICH OR LEAN)

Note: It is necessary to address all Continuous Memory Ignition and Misfire DTCs, if received during Continuous Memory testing, before addressing any KOER HO2S DTCs.

DTC/HO2S Reference List

HO2S-11 = DTCs P1131, P1132 and P1130
HO2S-21 = DTCs P1151, P1152 and P1150

Check intake air system for leaks, obstructions and damage.
Check air cleaner element, air cleaner housing for blockage.
Verify integrity of the PCV system.
Check for vacuum leaks.

Are any of the above concerns present?

Yes	No
REPAIR as necessary.	GO to H42 .

H41 DTCs P0171, P0172, P0174 AND P0175: FUEL SYSTEM AT THE CORRECTED FUEL TRIM

Note: It is necessary to address all Continuous Memory Ignition and Misfire DTCs, if received during Continuous Memory testing, before addressing any Fuel Trim DTCs.

DTCs HO2S Reference list:

HO2S-11 = DTCs P0171 and P0172
HO2S-21 = DTCs P0174 and P0175

Check intake air system for leaks, obstructions and damage.
Check air cleaner element, air cleaner housing for blockage.
Verify integrity of the PCV system.
Check for vacuum leaks.

Are any of the above concerns present?

Yes	No
REPAIR as necessary. COMPLETE KAM Reset.	GO to Pinpoint Test Step DC25 . If MAF reading is within specification, return to Pinpoint Test Step H42 .

H42 PERFORM KOER SELF-TEST

Disconnect fuel vapor hose from intake manifold and plug fitting at intake manifold.
Start engine and run at 2000 rpm for 5 minutes and return to idle.
Complete Key On Engine Running (KOER) Self-Test.

Are any HO2S DTCs P1127, P1128, P1129, P1131, P1132, P1151 or P1152 present?

Yes	No
KEY OFF. If DTC P1127, P1128 or P1129 is present, GO to Section 4 , Powertrain Diagnostic Trouble Code (DTC) Charts and REPAIR those DTCs first. If DTC P0131 or P0151 is present in Continuous Memory, GO to H27 . DTCs (P1131, P1130) or (P1151, P1150): GO to H43 . DTCs (P1132, P1130) or (P1152, P1150): GO to H49 .	KEY OFF. For Continuous Memory DTCs Only P1130, P1150, P0171, P0174, P0172 and P0175: GO to H52 . If DTC(s) P1132 and/or P1152 are no longer present, RECONNECT fuel vapor line. Vehicles experiencing KOER DTC 1132 or 1152: GO to HX22 . Vehicles experiencing KOER DTC 1131 or 1151: GO to HX58 . All others without recurring DTCs: Unable to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 .

Yes

KEY OFF. If DTC P1127, P1128 or P1129 is present, GO to Section 4 , Powertrain Diagnostic Trouble Code (DTC) Charts and REPAIR those DTCs first. If DTC P0131 or P0151 is present in Continuous Memory,

GO to H27 .

DTCs (P1131, P1130) or (P1151, P1150):

GO to H43 .

DTCs (P1132, P1130) or (P1152, P1150):

GO to H49 .

KEY OFF. For Continuous Memory DTCs Only P1130, P1150, P0171, P0174, P0172 and P0175:

GO to H52 .

If DTC(s) P1132 and/or P1152 are no longer present, RECONNECT fuel vapor line.

Vehicles experiencing KOER DTC 1132 or 1152:

GO to HX22 .

Vehicles experiencing KOER DTC 1131 or 1151:

GO to HX58 .

All others without recurring DTCs:

Unable to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 .

H43 HO2S CIRCUIT TEST (WITH LEAN DTCs)

Disconnect the HO2S related to the DTC.
Key on, engine off.
Access the correct HO2S PID.

Note: If arcing occurs (indicating a short), remove jumper and go to Pinpoint Test Step H47 (check fuse in the heater circuit).

Jumper the HO2S Signal circuit to the VPWR circuit at the HO2S vehicle harness connector.

Is the reading 1.30 volts or greater?

Yes	No
KEY OFF. CHECK SIG RTN circuit. GO to H44 .	KEY OFF. GO to H46 .

H44 CHECK SIGNAL RETURN CIRCUIT FOR OPEN

Measure resistance of HO2S SIG RTN circuit between the HO2S harness connector and the battery negative post.

Is the resistance reading less than 5.0 ohms?

Yes	No
GO to H52 .	GO to H45 .

H45 CHECK HO2S SIGNAL RETURN CIRCUIT FOR OPEN IN HARNESS

Disconnect PCM.
Measure resistance of HO2S SIG RTN circuit between the PCM harness connector pin and HO2S harness connector.

Is the resistance reading less than 5.0 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPAIR open circuit.

H46 CHECK HO2S SIGNAL AND HO2S GND CIRCUITS FOR OPEN IN HARNESS

Disconnect PCM.
Measure resistance of HO2S Signal circuit between PCM harness connector pin and the HO2S harness connector.

Is the resistance reading less than 5.0 ohms?

Yes	No
GO to H47 .	REPAIR open circuit.

H47 CHECK HO2S SIGNAL CIRCUIT FOR SHORT TO GROUND IN HARNESS

Measure resistance between the HO2S Signal and PWR GND circuits; and the HO2S Signal and SIG RTN circuits at the PCM harness connector.

Is each resistance greater than 10,000 ohms?

Yes	No
GO to H48 .	REPAIR short circuit.

H48 CHECK HO2S SIGNAL CIRCUIT FOR SHORT TO GROUND

Reconnect HO2S.
Measure resistance between HO2S Signal and PWR GND circuits and HO2S Signal and SIG RTN circuits at the PCM harness connector.

Is each resistance greater than 10,000 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPLACE HO2S.

H49 HO2S CIRCUIT CHECK (FOR RICH DTCS)

Disconnect the HO2S related to the DTC received.
Key on.
Access the correct HO2S PID(s).

Is the reading 0.2 volt or less?

Yes	No
KEY OFF. GO to H51 .	KEY OFF. GO to H50 .

H50 CHECK HO2S CIRCUIT FOR SHORT TO VPWR AND HO2S HEATER GROUND IN HARNESS

Disconnect PCM.
Measure resistance between the HO2S Signal and VPWR circuits; and HO2S Signal and HO2S HTR circuits at the PCM harness connector.

Is each resistance greater than 10,000 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPLACE HO2S.

H51 CHECK HO2S SIGNAL FOR SHORT TO HO2S HEATER CIRCUIT IN THE SENSOR

Suspect HO2S sensor connected.
Key on, engine off.

Note: HO2S displayed as O2S on Scan Tool.

Access HO2S PID corresponding to DTCs received.

Is the HO2S voltage greater than 0.45 volt?

Yes	No
KEY OFF. REPLACE HO2S.	KEY OFF. GO to H52 .

H52 CHECK FUEL PRESSURE

WARNING: THE FUEL SYSTEM IS PRESSURIZED WHEN THE ENGINE IS NOT RUNNING. TO PREVENT INJURY OR FIRE, USE CAUTION WHEN WORKING ON THE FUEL SYSTEM. BECOME FAMILIAR WITH THE WARNING CAUTION AND NOTE IN PINPOINT TEST HC BEFORE SERVICING.

Connect battery charger.
Install fuel pressure gauge.
Key on, engine off.
Access Output Test Mode and run the fuel pump to obtain maximum fuel pressure.
NOTE: The fuel pump will only operate for approximately 8 seconds when Output Test Mode is selected and activated.

FUEL PRESSURE CHART

Vehicle	kPa	PSI
Contour/Mystique, Cougar 2.5L	310-415	45-60
Continental	310-415	45-60
Escort/Tracer, Mustang, LS6/LS8	240-380	35-55
Ranger	386-496	56-72
Ranger (Flex Fuel)	380-517	55-75
All Others	207-310	30-45

Is the fuel pressure within the range for the vehicle being diagnosed?

Yes	No
KEY OFF. For mechanical and electronic returnless fuel systems: GO to H55 . All others: GO to H53 .	KEY OFF. GO to Pinpoint Test HC1 .

H53 CHECK FUEL SYSTEM FOR PRESSURE STABILITY

Cycle key on and off several times.
Verify there are no external leaks (repair as necessary).

Does the fuel pressure remain within 34 kPa (5 psi) of the highest reading after one minute?

Yes	No
For Continuous Memory DTCs P1130, P1150, P0171 and P0172, P0174 and P0175: GO to H54 . For HO2S DTCs displayed with misfire DTCs: GO to H56 . All other DTCs: GO to H59 .	GO to Pinpoint Test Step HC5 .

H54 CHECK FUEL SYSTEM FOR PRESSURE STABILITY WITH KEY ON

Cycle key on then off several times.
Key on and engine off, monitor fuel pressure gauge.

Does the fuel pressure remain within 34 kPa (5 psi) of the highest reading after 10 seconds?

Yes	No
For Continuous Memory DTCs P1130, P1150, P0171 and P0174: GO to H55 .	For DTC P0172 and P0175: GO to H55 .

H55 CHECK INJECTOR FAULT PIDS

Access INJ1F-INJ10F PIDs.

Note: If misfire DTCs are present, access only injector fault PIDs corresponding to misfire DTCs.

Is an injector(s) fault present?

Yes	No
GO to H56 .	All DTCs : GO to H59 .

H56 CHECK FUEL INJECTOR(S) AND HARNESS RESISTANCE

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Note: This erases Continuous Memory DTCs.

Disconnected PCM.

Note: Use the injector fault PID to determine the fuel injector circuit(s) requiring testing.

Measure resistance between suspect fuel injector and VPWR circuits at the PCM harness connector.

Is the resistance between 11.0-18.0 ohms?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	GO to H57 .

H57 CHECK FUEL INJECTOR HARNESS RESISTANCE

Disconnect fuel injector harness connector at the suspect fuel injector.
Measure resistance of VPWR circuit between PCM harness connector pin and the fuel injector harness connector.
Measure resistance of fuel injector circuit between PCM harness connector pin and the fuel injector harness connector.

Is each resistance less than 5.0 ohms?

Yes	No
GO to H58 .	REPAIR open harness circuit.

H58 CHECK FUEL INJECTOR HARNESS CIRCUIT FOR SHORT TO POWER AND GROUND

Disconnect PCM.
Suspect fuel injector disconnected.
Measure resistance between fuel injector signal and VPWR circuits; and between fuel injector signal and PWR GND circuits at the PCM harness connector.

Is each resistance greater than 10,000 ohms?

Yes	No
GO to H59 .	REPAIR short circuit.

H59 FLOW TEST FUEL INJECTOR(S)

Use the Rotunda Injector Tester, SBDS® Injector Tester or equivalent to flow test the fuel injectors according to the instructions for the fuel injector tester.

Is the leakage and flow within specification?

Yes	No
DTC P0171 and P0174: GO to H61 . DTC P0172 and P0175: Unable to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 . For DTC P1130 and P1150: GO to H61 . For DTC P1131 and P1151: GO to H60 . For DTC P1132 and P1152: GO to H64 .	REPLACE fuel injector.

H60 CHECK FOR SECONDARY AIR INTRUSION

Note: If the vehicle is not equipped with Secondary Air Injection System, GO to H61 .

An HO2S always lean condition can be caused by:

Leak in hoses from secondary air injection pump to engine.
Secondary Air diverted upstream of HO2S.

Disconnect secondary air injection hose(s) from engine and plug engine side of secondary air injection system.
Key on, engine running and at operating temperature.
Activate Key On, Engine Running (KOER) Self-Test.

Is DTC P1131 or P1151 present?

Yes	No
GO to H61 .	Cause of DTC(s) is in the Secondary Air Injection System. GO to HM7 for Secondary Air Injection System diagnostics.

H61 INSPECT INDUCTION SYSTEM FOR AIR LEAKS

Inspect the following areas for signs of air leaks:

Inlet tube(s) from air cleaner to the throttle body.
Gaskets which seal the upper and lower intake manifold.
Vacuum hoses and lines for cracks and proper connections.
PCV system.

Are there any signs of leaks or damage?

Yes	No
REPAIR as necessary.	CONTINUOUS DTCs P0171, P0174, P1130 or P1150: Unable to duplicate or identify fault at this time. GO to Pinpoint Test Step Z1 . DTCs P1131 and P1130 or P1151 and P1150: GO to H62 .

H62 CHECK CYLINDER COMPRESSION

Note: Use the Misfire DTC(s) displayed on prior DTC retrieval to determine which cylinder's compression to check.

Check cylinder compression. Refer to Engine, Section 303-00, 303-01 in the Workshop Manual.

Are cylinder compression readings within specification?

Yes	No
For DTCs P1131, P1130, P1151 and P1150: GO to H63 . For DTCs P1132 and P1152: GO to H64 . Misfire DTCs displayed with fuel control DTCs: GO to HD20 .	REPAIR as necessary.

H63 CHECK HO2S'S ABILITY TO GENERATE A VOLTAGE GREATER THAN 0.5 VOLT

Any vacuum or air leaks can cause DTCs P1131, P1130, P1151 and P1150.

Possible causes:

Leaking vacuum actuators.
Engine sealing (Intake and IAC).
EGR system (valve).
PCV system (hose and valve).
Unmetered air leaks between throttle body and mass air flow (MAF) sensor assembly.
Silicone contaminated HO2S.

Inspect HO2S harness for chafing, burned wires or other damage and repair as necessary.
Unplug the suspect HO2S.
Connect digital multimeter to the HO2S Signal and HO2S SIG RTN or HO2S GND at the HO2S sensor connector.
Run engine at 2000 rpm for three minutes.
Rerun KOER Self-Test and monitor HO2S voltage.

Is the voltage greater than 0.5 volt during or at the end of Self-Test?

Yes	No
KEY OFF. GO to H70 .	KEY OFF. REPLACE HO2S.

H64 ATTEMPT TO GENERATE DTC P1131 OR P1151

HO2S disconnected.
Jumper HO2S Signal at the HO2S harness vehicle connector to the battery negative post.
Activate Key On Engine Running (KOER) Self-Test.

Is DTC P1131 or P1151 present?

Yes	No
KEY OFF. REMOVE jumper. GO to H65 .	KEY OFF. REMOVE jumper. RECONNECT HO2S. DISCONNECT PCM. INSPECT both ends of connector for damaged or pushed out pins, moisture, corrosion, loose pins and REPAIR as necessary. If OK, REPLACE PCM (refer to Section 2 , Flash EEPROM).

H65 HO2S SENSOR VOLTAGE CHECK

HO2S disconnected.
Connect digital multimeter to HO2S SIG circuit and HO2S SIG RTN at the HO2S sensor connector.
Disconnect vacuum hose from vacuum tree.
Start engine and run at 2000 rpm.

Does the voltage reading indicate less than 0.4 volt within 30 seconds?

Yes	No
KEY OFF. RECONNECT vacuum hose and HO2S. GO to H70 .	KEY OFF. REPLACE HO2S.

H70 MONITOR HO2S (PID) FOR PROPER SWITCHING

Key on, engine running.
Engine at operating temperature.

Note: HO2S displayed as O2S on Scan Tool.

Monitor suspect HO2S PID.
Wiggling, bending, and shaking small sections of the Electronic Engine Control harness from the PCM to the HO2S.

Did the HO2S voltage stay high (greater than 0.45 volt) or low (less than 0.45 volt)?

Yes	No
KEY OFF. ISOLATE cause of lack of HO2S switches and repair.	KEY OFF. GO to H71 .

H71 TEST DRIVE WHILE MONITORING HO2S PID FOR PROPER SWITCHING

Note: This test step requires an observer to monitor PID for proper operation.

Access HO2S PID.
While observer views PID, test drive vehicle under different road conditions in an attempt to simulate the original fault.

Does HO2S appear to switch properly?

Yes	No
KEY OFF. UNABLE to duplicate fault. Testing complete at this time.	KEY OFF. REPLACE HO2S.

H80 DTC P0136 AND P0156 MONITOR DOWNSTREAM HO2S OUTPUT VOLTAGE FOR ACTIVITY. DTCs P1137, P1138, P1157 AND/OR P1158 INDICATE LACK OF HO2S SWITCHING

Note: Refer to the PCM connector pin numbers in the beginning of this pinpoint test.

Note: It is necessary to address all Continuous Memory Ignition and Misfire DTCs, if received during Continuous Memory testing, before addressing any KOER HO2S DTCs.

DTC P0136, P1137 and P1138=HO2S-12
DTC P0156, P1157 and P1158=HO2S-22

Visually inspect for:

pinched, shorted, and corroded wiring and pins
crossed sensor wires
exhaust leaks
contaminated or damaged sensor

Is any concern present?

Yes	No
REPAIR as necessary.	Continuous Memory DTC P0136 and P0156: GO to H81 . All others: GO to H82 .

H81 CHECK FOR KOER DTCS P1137, P1157, P1138 AND P1158

Key on.
Engine at 2000 rpm for 3 minutes.
Activate KOER Self-Test.
Check for DTCs.

Is DTC P1137, P1138, P1157 or P1158 present?

Yes	No
KEY OFF. GO to H82 .	KEY OFF. For DTC P0136 and P0156: Unable to duplicate or identify at this time. GO to Pinpoint Test Step Z1 .

H82 CHECK EXHAUST SYSTEM FOR LEAKS

Note: Any exhaust leaks between the engine and the end of the catalyst can cause DTC P0136 and P0156.

Place vehicle on a hoist, transmission in PARK, emergency brake applied, raise vehicle.
Inspect the following:

Exhaust flanges for leaks.
HO2S torque.
Check for punctures and cracks in catalyst and pipes leading to them.

Are there any exhaust leaks?

Yes	No
REPLACE or REPAIR as required.	GO to H83 .

H83 CHECK HO2S HARNESS CIRCUIT FOR SHORT TO VPWR AND GROUND

Disconnect PCM.
Disconnect suspect HO2S.
Measure resistance between HO2S Signal and SIG RTN circuits at the PCM harness connector.
Measure resistance between HO2S Signal circuit and VPWR and VREF circuits at the PCM harness connector.
Measure resistance between HO2S Signal circuit and PWR GND circuit at the PCM harness connector.

Is resistance greater than 10,000 ohms?

Yes	No
GO to H84 .	REPAIR short in harness.

H84 CHECK HO2S SIGNAL CIRCUIT AND HO2S SIGNAL RETURN CIRCUITS FOR OPEN IN HARNESS

Measure resistance of HO2S Signal circuit between the PCM harness connector pin and the HO2S harness connector.
Measure resistance of SIG RTN circuit between the PCM harness connector pin and HO2S SIG RTN vehicle harness connector.

Is the resistance reading less than 5.0 ohms?

Yes	No
GO to H85 .	REPAIR open circuit.

H85 CHECK HO2S CIRCUIT VOLTAGE

Connect PCM.
Suspect HO2S connected to harness.
Key on, engine off.

Note: HO2S displayed as O2S on Scan Tool.

Access the correct HO2S PID.

Is the voltage greater than 1.5 volts?

Yes	No
KEY OFF. GO to H88 .	KEY OFF. GO to H86 .

H86 CHECK HO2S GROUND CIRCUIT IN THE PCM

Disconnect PCM.
Measure resistance between SIG RTN and PWR GND circuits at the PCM connector.

Is the resistance reading less than 5.0 ohms?

Yes	No
GO to H87 .	REPLACE PCM (refer to Section 2 , Flash EEPROM).

H87 HO2S CIRCUIT CHECK

PCM connected.
Suspect HO2S disconnected.
Jumper VPWR to HO2S signal circuit at the HO2S harness connector.
Key on.
Access HO2S PID.

Is the PID value greater than 1.5 volts?

Yes	No
REPLACE HO2S.	REPLACE PCM (refer to Section 2 , Flash EEPROM).

H88 CHECK FOR OVER VOLTAGE ON THE HO2S CIRCUIT IN THE PCM

Key on.
HO2S disconnected.
Measure voltage between SIG RTN circuit at the HO2S harness connector and battery negative post.
Measure voltage between HO2S SIG circuit at the HO2S harness connector and battery negative post.

Are either voltage readings greater than 1.5 volts?

Yes	No
REPLACE PCM (refer to Section 2 , Flash EEPROM).	REPLACE HO2S.

H100 KOER DTC P1127

Key on, engine on.
Access all HO2S heaters and HO2S heater monitor PIDs.

Do all PIDs indicate ON?

Yes	No
Engine still operating. PERFORM KOER Self-Test.	Operate the engine until all PIDs indicate on. PERFORM KOER Self-Test.

H110 DTCS P1128 AND P1129 KOER

Note: Refer to the PCM harness connector pin numbers in the beginning of this pinpoint test.

P1128 refer to the upstream HO2S.
P1129 refer to the downstream HO2S.

Visually inspect vehicle HO2S harness connector(s) for any indication of being crossed (stretched wires, wire harnesses not mounted properly).

Are there crossed connections or wires?

Yes	No
REPAIR as necessary.	GO to H111 .

H111 VERIFY PROPER HO2S SIGNAL PIN LOCATION

PCM disconnected.
Disconnect both of the suspect HO2S sensors from the vehicle harness connector.

P1128 = HO2S 11/21 Upstream
P1129 = HO2S 12/22 Downstream

Measure resistance of HO2S signal circuits between PCM harness connector pins and HO2S harness connector.

Is the resistance less than 5.0 ohms?

Yes	No
Unable to duplicate or identify at this time. GO to Pinpoint Test Step Z1 .	CONNECT HO2S connector to proper HO2S signal pins in the PCM harness connector or HO2S harness connectors. RERUN Quick Test.